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Abstract:

A power control device that controls electric power supplied from an
external power supply to a vehicle includes: a switching unit that
switches a supply voltage value of the external power supply; and a
control unit that generates a signal, indicating an allowable current
value of the external power supply, to transmit the signal to the
vehicle, and that controls the switching unit to thereby control the
supply voltage value, wherein the control unit changes the signal and the
supply voltage value on the basis of a given electric power command
value.

Claims:

1. A power control device that controls electric power supplied from an
external power supply to a vehicle, comprising: a switching unit that
switches a supply voltage value of the external power supply; and a
control unit that generates a signal, indicating an allowable current
value of the external power supply, to transmit the signal to the
vehicle, and that controls the switching unit to thereby control the
supply voltage value, wherein the control unit changes the signal and the
supply voltage value on the basis of a given electric power command
value.

2. The power control device according to claim 1, wherein the control
unit sets a current command value and a voltage command value on the
basis of the electric power command value, generates the signal so that
the allowable current value is equal to the current command value, and
controls the switching unit so that the supply voltage value is equal to
the voltage command value.

3. The power control device according to claim 2, wherein the allowable
current value has a lower limit value and an upper limit value, and the
control unit sets the current command value and the voltage command value
so that the current command value falls within the range from the lower
limit value to the upper limit value and the product of the current
command value and the voltage command value is equal to the electric
power command value.

4. The power control device according to claim 3, wherein the switching
unit is configured to switch the supply voltage value to any one of a
first voltage value and a second voltage value that is higher than the
first voltage value, when the electric power command value is smaller
than a threshold that is the product of the second voltage value and the
lower limit value, the control unit sets the voltage command value to the
first voltage value and sets the current command value to a value
obtained by dividing the electric power command value by the first
voltage value, and when the electric power command value is larger than
the threshold, the control unit sets the voltage command value to the
second voltage value and sets the current command value to a value
obtained by dividing the electric power command value by the second
voltage value.

5. The power control device according to claim 3, wherein the switching
unit is configured to switch the supply voltage value to any one of a
first voltage value, a second voltage value that is higher than the first
voltage value, and a third voltage value that is higher than the second
voltage value, when the electric power command value is smaller than a
first threshold that is the product of the second voltage value and the
lower limit value, the control unit sets the voltage command value to the
first voltage value and sets the current command value to a value
obtained by dividing the electric power command value by the first
voltage value, when the electric power command value falls within the
range from the first threshold to a second threshold that is the product
of the third voltage value and the lower limit value, the control unit
sets the voltage command value to the second voltage value and sets the
current command value to a value obtained by dividing the electric power
command value by the second voltage value, and when the electric power
command value is larger than the second threshold, the control unit sets
the voltage command value to the third voltage value and sets the current
command value to a value obtained by dividing the electric power command
value by the third voltage value.

6. The power control device according to claim 1, wherein the switching
unit is a switch circuit that is provided in any location of a power
supply line extending from the external power supply.

7. The power control device according to claim 1, wherein the signal is a
pilot signal that oscillates with a pulse width corresponding to the
allowable current value, the control unit transmits the pilot signal to
the vehicle via a communication line, and the vehicle executes control
for charging an electrical storage device equipped for the vehicle on the
basis of the pilot signal received from the control unit.

8. The power control device according to claim 1, wherein the allowable
current value is current value that is supplied from the external power
supply to the vehicle.

9. A power control method that controls electric power supplied from an
external power supply to a vehicle, comprising: generating a signal,
indicating an allowable current value of the external power supply, to
transmit the signal to the vehicle; controlling a switching unit that
switches a supply voltage value of the external power supply to thereby
control the supply voltage value; and changing the signal and the supply
voltage value on the basis of a given electric power command value.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a power control device and power control
method that control electric power supplied from an external power supply
to a vehicle.

[0003] 2. Description of the Related Art

[0004] An electromotive vehicle, such as an electric vehicle and a hybrid
electric vehicle, is in practical use. The electromotive vehicle is
propelled by a motor that is driven by electric power stored in an
electrical storage device. In addition, in recent years, development of a
so-called plug-in vehicle has been proceeding. The plug-in vehicle
includes a system that charges an electrical storage device with power
supplied from an external power supply called, a charging station, or the
like.

[0005] In connection with charging control over such a plug-in vehicle,
for example, Japanese Patent Application Publication No. 6-245325
(JP-A-6-245325) describes a technique for simplifying charging operation.
An electric vehicle described in JP-A-6-245325 includes a battery, a
charging line for charging the battery, and a communication device that
is connected to the charging line. On the other hand, an external power
supply that supplies electric power to the electric vehicle includes a
charging line, and a communication device that is connected to the
charging line. When a connector of the electric vehicle is connected to a
connector of the external power supply, the communication device of the
electric vehicle transmits charging information, such as the type or
voltage of the battery, to the communication device of the external power
supply via the charging lines. The communication device of the external
power supply charges the battery of the electric vehicle automatically in
an optimal condition in accordance with the charging information from the
electric vehicle. By so doing, charging operation for charging the
battery of the electric vehicle may be simplified.

[0006] As described above, JP-A-6-245325 describes that communication is
carried out between the electric vehicle and the external power supply
and then control for charging the electric vehicle is executed at the
side of the external power supply on the basis of the communication
information. However, JP-A-6-245325 does not describe specific details of
the communication information and a method of generating the
communication information.

[0007] Particularly, the range of information that is transmittable by a
signal transmitted from the external power supply to the electromotive
vehicle (for example, the range of allowable current value of the
external power supply, which is transmittable by a pilot signal) is
limited to a value that falls within a predetermined range because of the
specifications of the signal or the physical requirements of the external
power supply. Therefore, there is a problem that a power range that
allows control for charging the electromotive vehicle is limited.
JP-A-6-245325 describes nothing about the above problem or measures
therefor.

SUMMARY OF INVENTION

[0008] The invention provides a power control device and power control
method that are able to minutely control electric power supplied from an
external power supply to a vehicle using a signal generated by the
external power supply.

[0009] A first aspect of the invention provides a power control device
that controls electric power supplied from an external power supply to a
vehicle. The power control device includes: a switching unit that
switches a supply voltage value of the external power supply; and a
control unit that generates a signal, indicating an allowable current
value of the external power supply, to transmit the signal to the
vehicle, and that controls the switching unit to thereby control the
supply voltage value, wherein the control unit changes the signal and the
supply voltage value on the basis of a given electric power command
value.

[0010] The control unit may set a current command value and a voltage
command value on the basis of the electric power command value. In this
case, the control unit may generate the signal so that the allowable
current value is equal to the current command value, and may control the
switching unit so that the supply voltage value is equal to the voltage
command value.

[0011] The allowable current value may have a lower limit value and an
upper limit value. In this case, the control unit may set the current
command value and the voltage command value so that the current command
value falls within the range from the lower limit value to the upper
limit value and the product of the current command value and the voltage
command value is equal to the electric power command value.

[0012] The switching unit may be configured to switch the supply voltage
value to any one of a first voltage value and a second voltage value that
is higher than the first voltage value. In this case, when the electric
power command value is smaller than a threshold that is the product of
the second voltage value and the lower limit value, the control unit may
set the voltage command value to the first voltage value and may set the
current command value to a value obtained by dividing the electric power
command value by the first voltage value, and, when the electric power
command value is larger than the threshold, the control unit may set the
voltage command value to the second voltage value and may set the current
command value to a value obtained by dividing the electric power command
value by the second voltage value.

[0013] The switching unit may be configured to switch the supply voltage
value to any one of a first voltage value, a second voltage value that is
higher than the first voltage value, and a third voltage value that is
higher than the second voltage value. In this case, when the electric
power command value is smaller than a first threshold that is the product
of the second voltage value and the lower limit value, the control unit
may set the voltage command value to the first voltage value and may set
the current command value to a value obtained by dividing the electric
power command value by the first voltage value, when the electric power
command value falls within the range from the first threshold to a second
threshold that is the product of the third voltage value and the lower
limit value, the control unit may set the voltage command value to the
second voltage value and may set the current command value to a value
obtained by dividing the electric power command value by the second
voltage value, and, when the electric power command value is larger than
the second threshold, the control unit may set the voltage command value
to the third voltage value and may set the current command value to a
value obtained by dividing the electric power command value by the third
voltage value.

[0014] The switching unit may be a switch circuit that is provided in any
location of a power supply line extending from the external power supply.

[0015] The signal may be a pilot signal that oscillates with a pulse width
corresponding to the allowable current value. In addition, the control
unit may transmit the pilot signal to the vehicle via a communication
line. In addition, the vehicle may execute control for charging an
electrical storage device equipped for the vehicle on the basis of the
pilot signal received from the control unit.

[0016] A second aspect of the invention provides a power control method
that controls electric power supplied from an external power supply to a
vehicle. The power control method includes: generating a signal,
indicating an allowable current value of the external power supply, to
transmit the signal to the vehicle; controlling a switching unit that
switches a supply voltage value of the external power supply to thereby
control the supply voltage value; and changing the signal and the supply
voltage value on the basis of a given electric power command value.

[0017] According to the aspects of the invention, it is possible to
minutely control electric power supplied from an external power supply to
a vehicle using a signal generated by the external power supply.

BRIEF DESCRIPTION OF DRAWINGS

[0018] The features, advantages, and technical and industrial significance
of this invention will be described below with reference to the
accompanying drawings, in which like numerals denote like elements, and
wherein:

[0019] FIG. 1 is a schematic view of a charging station that is equipped
with a power control device according to a first embodiment;

[0020] FIG. 2 is a cross-sectional view of a charging cable according to
the first embodiment;

[0021] FIG. 3 is a schematic view of a switching device;

[0022] FIG. 4 is a waveform chart of a pilot signal;

[0023] FIG. 5 is a functional block diagram of an ECU;

[0024] FIG. 6 is a first map used to calculate a voltage command value and
a current command value according to the first embodiment;

[0025] FIG. 7 is a second map used to calculate a duty ratio D of the
pilot signal;

[0026] FIG. 8 is a flowchart that shows the control procedure of the ECU;

[0027] FIG. 9 is a first map that is used to calculate a voltage command
value and a current command value according to an alternative embodiment
to the first embodiment;

[0028] FIG. 10 is a schematic view of a charging station that is equipped
with a power control device according to a second embodiment;

[0029] FIG. 11 is a cross-sectional view of a charging cable according to
the second embodiment; and

[0030] FIG. 12 is a first map used to calculate a voltage command value
and a current command value according to the second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0031] Hereinafter, embodiments of the invention will be described in
detail with reference to the accompanying drawings. Like reference
numerals in the drawings denote the same or corresponding components, and
the description thereof will not be repeated. In the following
description, specific values are, for example, used for a voltage value,
a current value and an electric power value; however, the aspect of the
invention is not limited to those specific values.

First Embodiment

[0032] FIG. 1 is a schematic view of a charging station 10 that is
equipped with a power control device according to a first embodiment of
the invention. The charging station 10 is an alternating-current power
supply that is exclusively provided in order to charge an electrical
storage device equipped for an electromotive vehicle, such as a vehicle
1. Note that the charging station 10 may be a direct-current power
supply.

[0033] The vehicle 1 is an electromotive vehicle that is propelled by a
motor (not shown) driven by electric power of an electrical storage
device B. The vehicle 1 may be an electric vehicle that includes only a
motor as a driving source or may be a hybrid electric vehicle that
includes a motor and an engine.

[0034] The vehicle 1 is a so-called plug-in vehicle, and includes a
charging system for charging the electrical storage device B with
alternating-current power supplied from the external charging station 10.
The charging system includes an inlet 2, a charger 3 and an ECU 4. The
inlet 2 is configured to be connected with a connector 12 of a charging
cable CA extending from the charging station 10. The charger 3 converts
alternating-current power supplied from the charging station 10 to
direct-current power that may be used to charge the electrical storage
device B and then supplies the direct-current power to the electrical
storage device B in accordance with a control signal from the ECU 4.

[0035] When the connector 12 of the charging cable CA is connected to the
inlet 2 of the vehicle 1, a pilot signal CPLT (which will be described
later) generated by an ECU 100 of the charging station 10 is input to the
ECU 4 via the charging cable CA and the inlet 2. The ECU 4 controls the
charger 3 on the basis of information, such as the pilot signal CPLT, to
thereby execute control for charging the electrical storage device B.

[0036] On the other hand, the charging station 10 includes a commercial
power supply 11, a switching device SW, the charging cable CA and the ECU
100.

[0037] The commercial power supply 11 is a so-called single-phase
three-wire system alternating-current power supply that is widely used in
Japan, and the like.

[0038] One end of the charging cable CA is connected to the switching
device

[0039] SW via a connecting portion 13, and the other end of the charging
cable CA is connected to the connector 12. The connector 12 is configured
to be connected with the inlet 2 of the vehicle 1. Note that it is
applicable that the connecting portion 13 is formed of a connector and
then the charging cable CA and the charging station 10 are detachable
from each other.

[0040] FIG. 2 is a cross-sectional view of the charging cable CA, taken
along the line II-II in FIG. 1. As shown in FIG. 2, the charging cable CA
is formed so that power lines L(-) and L(+) that extend from the
switching device SW, a ground line Lg, and a pilot signal line Lc that
extends from the ECU 100 are tied in a bundle as one cable.

[0041] Referring back to FIG. 1, the switching device SW is provided
between the commercial power supply 11 and the charging cable CA. The
switching device SW switches the voltage, which is supplied from the
charging station 10 to the vehicle 1 via the charging cable CA
(hereinafter, simply referred to as supply voltage), to any one of a
voltage V1 and a voltage V2. Note that, in the first embodiment, the case
where the voltage V1 is 100 volts and the voltage V2 is 200 volts will be
described as an example.

[0042] The commercial power supply 11 and the switching device SW are
connected by power lines L1 and L2 and a neutral line Ln. The power line
L1 is supplied with 100-volt alternating-current power from the
commercial power supply 11. The power line L2 is supplied from the
commercial power supply 11 with 100-volt alternating-current power, which
is shifted by 180 degrees in phase from that of the power line L1.

[0043] FIG. 3 schematically shows the inside of the switching device SW.
The power line L(+) of the charging cable CA is directly coupled to the
power line L1 from the commercial power supply 11.

[0044] The switching device SW has a switch circuit S1 that connects the
power line L(-) of the charging cable CA to any one of the neutral line
Ln and the power line L2 that extend from the commercial power supply 11.
The switch circuit S1. switches a connected destination of the power line
L(-) to any one of the neutral line Ln and the power line L2 in
accordance with a switching signal S transmitted from the ECU 100 via a
communication line L4.

[0045] When the connected destination of the power line L(-) is the
neutral line Ln, the supply voltage is 100 volts (voltage V1) that is a
potential difference between the power line L(+) and the power line L(-).

[0046] On the other hand, when the connected destination of the power line
L(-) is the power line L2, the supply voltage is 200 volts (voltage V2)
that is a potential difference between the power line L(+) and the power
line L(-).

[0047] Referring back to FIG. 1, the ECU 100 generates a switching signal
S and then transmits the switching signal S to the switching device SW,
and also generates a pilot signal CPLT and then transmits the pilot
signal CPLT to the vehicle 1 via the pilot signal line Lc. The pilot
signal CPLT is a signal that indicates an allowable current value of the
charging station 10 (current value that the charging station 10 is able
to supply to an electromotive vehicle, such as the vehicle 1, via the
charging cable CA). As the pilot signal CPLT is transmitted to the
vehicle 1, the allowable current value of the charging station 10 is
transmitted to the vehicle 1.

[0048] FIG. 4 is a waveform chart of the pilot signal CPLT generated by
the ECU 100. The pilot signal CPLT oscillates at a given period T (for
example, 1 kHz). A duty ratio D that is the ratio of a pulse width Ton to
the period T (that is, D=Ton/T×100 (%)) is set to a value
corresponding to the allowable current value of the charging station 10.

[0049] The ECU 4 of the vehicle 1 receives the pilot signal CPLT via the
inlet 2, and detects the duty ratio D of the received pilot signal CPLT
to thereby acquire the allowable current value of the charging station
10, and then controls the charger 3 in accordance with the acquired
allowable current value. Therefore, the ECU 4 of the vehicle 1 is able to
control electric power for charging the vehicle 1 using the pilot signal
CPLT. However, normally, a specification lower limit value is set for the
current value that is transmittable by the duty ratio D of the pilot
signal CPLT. In addition, the allowable current value of the charging
station 10 also has an upper limit value (current capacity) that is
determined depending on physical requirements of the charging cable CA,
the inlet 2, and the like. Thus, the current value that is transmittable
by the duty ratio D of the pilot signal CPLT is limited to a value that
falls within the range between the above described lower limit value and
upper limit value.

[0050] For example, when the lower limit value is 6 amperes and the upper
limit value is 12 amperes, the available current value is limited to a
value that falls within the range from 6 amperes to 12 amperes. When the
supply voltage is fixed to 100 volts in such a situation, a controllable
charging electric power value is limited to a value that falls within the
narrow range from 600 watts (which is equal to 100 volts multiplied by 6
amperes) to 1200 watts (which is equal to 100 volts multiplied by 12
amperes). It is presumable that this may result in insufficient charging
control.

[0051] In order to solve such a problem, in the first embodiment, the
above described switching device SW is provided, and the ECU 100 executes
both variable control of the duty ratio D of the pilot signal CPLT and
switching control of the supply voltage (control of the switching device
SW) on the basis of an electric power command value Pcom input from an
outside by user's operation, or the like.

[0052] FIG. 5 is a functional block diagram of a portion of the ECU 100,
related to variable control of the duty ratio D and switching control of
the supply voltage. Note that the functional blocks shown in FIG. 5 may
be implemented in such a manner that hardware (electronic circuit, or the
like) having the functions is provided for the ECU 100 or may be
implemented in such a manner that software processing (execution of a
program, or the like) corresponding to the functions is performed by the
ECU 100.

[0053] The ECU 100 includes a calculation unit 110, a storage unit 120, a
conversion unit 130, a first generation unit 140 and a second generation
unit 150.

[0054] The calculation unit 110 refers to a first map stored in the
storage unit 120 to thereby calculate a voltage command value Vcom and a
current command value Icom corresponding to the electric power command
value Pcom. Here, the electric power command value Pcom is a command
value of electric power supplied from the charging station 10 to the
vehicle 1, and is input from an outside to the calculation unit 110
through user's operation, or the like. The voltage command value Vcom is
a command value of supply voltage. The current command value Icom is a
value corresponding to the allowable current value of the charging
station 10, and is a value used to determine the duty ratio D of the
pilot signal CPLT.

[0055] FIG. 6 shows a first map used to calculate the voltage command
value Vcom and the current command value Icom. Note that, in the
following description, P1min and P2min respectively denote electric power
values when the supply current is a lower limit value and the supply
voltages are the voltages V1 and V2, and P1max and P2max respectively
denote electric power values when the supply current is an upper limit
value and the supply voltages are the voltages V1 and V2. In the first
embodiment, because the voltage V1 is 100 volts, the voltage V2 is 200
volts, the lower limit value of the supply current is 6 amperes and the
upper limit value of the supply current is 12 amperes, P1min is 0.6
kilowatts (100 volts multiplied by 6 amperes), P1max is 1.2 kilowatts
(100 volts multiplied by 12 amperes), P2min is 1.2 kilowatts (200 volts
multiplied by 6 amperes) and P2max is 2.4 kilowatts (200 volts multiplied
by 12 amperes).

[0056] The first map prestores the voltage command value Vcom and current
command value Icom corresponding to the electric power command value
Pcom.

[0057] The voltage command value Vcom is set to the voltage V1 when the
electric power command value Pcom is smaller than a threshold Pb, and is
set to the voltage V2 when the electric power command value Pcom is
larger than the threshold Pb. Here, the threshold Pb is set to the
electric power value P2min (that is, the product of the voltage V2 and
the lower limit value). In the example shown in FIG. 6, the threshold Pb
is the electric power value P2min and is 1.2 kilowatts. Note that, in the
example shown in FIG. 6, the electric power value P1max is also 1.2
kilowatts, and the threshold Pb is the same value as the electric power
value P1max.

[0058] On the other hand, the current command value Icom is set so as to
satisfy the relationship that Icom is equal to Pcom divided by Vcom when
Icom ranges from the lower limit value to the upper limit value. In the
example shown in FIG. 6, when the electric power command value Pcom falls
within the range from the threshold Pa to the threshold Pb, the current
command value Icom is set to Pcom divided by V1, and, when the electric
power command value Pcom falls within the range from the threshold Pb to
the threshold Pc, the current command value Icom is set to Pcom divided
by V2. Here, the threshold Pa is set to the electric power value P1min
(the product of the voltage V1 and the lower limit value), and the
threshold Pc is set to the electric power value P2max (the product of the
voltage V2 and the upper limit value). In the example shown in FIG. 6,
the threshold Pa is set to 0.6 kilowatts, and the threshold Pc is set to
2.4 kilowatts.

[0059] The range in which the electric power command value Pcom is smaller
than the threshold Pa is an uncontrollable range in which the current
command value Icom is smaller than the lower limit value. Within the
uncontrollable range, the current command value Icom is not set. In
addition, the range in which the electric power command value Pcom is
larger than the threshold Pc is a control prohibiting range in which the
current command value Icom exceeds the upper limit value. Within the
control prohibiting range, the current command value Icom is not set.

[0060] When the voltage command value Vcom is fixed to the voltage V1, the
current command value Icom exceeds the upper limit value when the
electric power command value Pcom exceeds the threshold Pb. Thus, the
controllable power range is limited to the range indicated by R1 in FIG.
6, that is, the range from P1min to P1max.

[0061] In addition, when the voltage command value Vcom is fixed to the
voltage V2, the current command value Icom is lower than the lower limit
value when Pcom is smaller than the threshold Pb. Thus, the controllable
power range is limited to the range indicated by R2 in FIG. 6, that is,
the range from P2min to P2max.

[0062] Then, in the first map, when the electric power command value Pcom
is smaller than the threshold Pb, the voltage command value Vcom is set
to the voltage V1;

[0063] whereas, when the electric power command value Pcom exceeds the
threshold Pb, the voltage command value Vcom is switched to the voltage
V2 higher than the voltage V 1. By so doing, even when the electric power
command value Pcom exceeds the threshold Pb, the current command value
Icom may be suppressed to a value lower than the upper limit value when
the electric power command value Pcom is lower than the threshold Pc.

[0064] Therefore, the controllable power range in the first embodiment is
the range indicated by R3 in FIG. 6, that is, the range from P1min to
P2max, and is wider than the range R1 or the range R2 for which the
voltage command value Vcom is fixed to the voltage V1 or V2.

[0065] Referring back to FIG. 5, the conversion unit 130 refers to a
second map stored in the storage unit 120 to thereby convert the current
command value Icom, calculated by the calculation unit 110, to the duty
ratio D of the pilot signal CPLT.

[0066] FIG. 7 shows the second map used to calculate the duty ratio D of
the pilot signal CPLT. The second map prestores the duty ratio D of the
pilot signal CPLT corresponding to the current command value Icom. In the
second map, as the current command value Icom increases, the duty ratio D
of the pilot signal CPLT is increased. However, the current command value
Icom is limited to a value between the above described lower limit value
and upper limit value. Thus, as shown in FIG. 7, the duty ratio D of the
pilot signal CPLT is also controlled to a value that falls within the
range from a minimum value Dmin to a maximum value Dmax.

[0067] Referring back to FIG. 5, the first generation unit 140 generates
the pilot signal CPLT having the duty ratio D calculated by the
conversion unit 130, and transmits the pilot signal CPLT to the vehicle 1
via the pilot signal line Lc.

[0068] On the other hand, the second generation unit 150 generates the
switching signal S corresponding to the voltage command value Vcom
calculated by the calculation unit 110, and transmits the switching
signal S to the switching device SW. By so doing, the supply voltage
becomes a value corresponding to the voltage command value Vcom.

[0069] FIG. 8 is a flowchart that shows the control procedure for
implementing the functions of the ECU 100. Steps (hereinafter step is
abbreviated to "S") of the following flowchart are basically implemented
through software processing executed by the ECU 100; however, the steps
may be implemented by hardware, such as an electronic circuit provided
for the ECU 100. Note that the process is repeatedly executed at a
prescribed cycle time.

[0070] In S1, the ECU 100 determines whether the electric power command
value Pcom is input. When the electric power command value Pcom is input
(YES in S1), the process proceeds to S2. When the determination is
negative (NO in S1), the process ends.

[0071] In S2, the ECU 100 refers to the first map shown in FIG. 6, and
calculates the voltage command value Vcom and current command value Icom
corresponding to the electric power command value Pcom.

[0072] In S3, the ECU 100 refers to the second map shown in FIG. 7, and
calculates the duty ratio D of the pilot signal CPLT corresponding to the
current command value Icom.

[0073] In S4, the ECU 100 generates the pilot signal CPLT having the duty
ratio D calculated in S3.

[0074] In S5, the ECU 100 determines whether the voltage command value
Vcom is the voltage V1. When the voltage command value Vcom is the
voltage V1 (YES in S5), the process proceeds to S6. When the
determination is negative (NO in S5), the process proceeds to S7.

[0075] In S6, the ECU 100 sets the supply voltage to the voltage V1. That
is, the ECU 100 generates the switching signal S for causing the switch
circuit S1 of the switching device SW to enter a state where the power
line L(-) is connected to the neutral line Ln, and then transmits the
switching signal S to the switching device SW.

[0076] In S7, the ECU 100 sets the supply voltage to the voltage V2. That
is, the ECU 100 generates the switching signal S for causing the switch
circuit S1 of the switching device SW to enter a state where the power
line L(-) is connected to the power line L2, and then transmits the
switching signal S to the switching device SW.

[0077] In S8, the ECU 100 transmits the pilot signal CPLT, generated in
S4, to the vehicle 1 via the pilot signal line Lc.

[0078] As described above, in the first embodiment, the charging station
that supplies electric power to an electromotive vehicle is provided with
the switching device SW for switching the supply voltage. Then, the ECU
100 installed in the charging station executes both variable control of
the duty ratio D of the pilot signal CPLT and switching control of the
supply voltage (control of the switching device SW) on the basis of the
electric power command value Pcom input from an outside. Therefore, it is
possible to expand the controllable power range while using the existing
pilot signal CPLT and pilot signal line Lc, so further detailed power
control is possible.

Alternative Embodiment to First Embodiment

[0079] In the above described first embodiment, the upper limit value
(current capacity) of the supply current is 12 amperes; however, the
upper limit of the supply current may be larger than 12 amperes.

[0080] FIG. 9 shows a first map when the upper limit value of the supply
current is 20 amperes. Note that, in FIG. 9, the voltage V1, the voltage
V2 and the lower limit value of supply current are respectively 100
volts, 200 volts and 6 amperes as in the case of the first embodiment.

[0081] In this case, the electric power value P1max is set to 2 kilowatts
(which is equal to 100 volts multiplied by 20 amperes), the electric
power value P2min is 1.2 kilowatts (which is equal to 200 volts
multiplied by 6 amperes), the electric power value P2min is smaller than
the electric power value P1max, and the threshold Pb is set to 1.2
kilowatts that is the electric power value P2min.

[0082] That is, when the electric power command value Pcom falls within
the range of the electric power value P2min to P1max, the supply voltage
may be set to any one of the voltages V1 and V2; however, when the
threshold Pb is set to the electric power value P2min smaller than the
electric power value P1max, the supply voltage is preferentially set to
the voltage V2 that is larger than the voltage V1. When the supply
voltage is set to the voltage V2, the current command value Icom is
reduced even when the same electric power is supplied to thereby make it
possible to suppress loss (generation of Joule heat, or the like) in
process of supplying electric power as compared with when the supply
voltage is set to the voltage V1, so it is possible to improve charging
efficiency.

Second Embodiment

[0083] In the first embodiment, the case where the supply voltage is set
to any one of the two voltages V1 and V2 is described. In contrast to
this, in a second embodiment, the case where the supply voltage is set to
any one of three voltages V1, V2 and V3 will be described.

[0084] FIG. 10 is a schematic view of a charging station 10a that includes
a power control device according to the second embodiment.

[0085] The charging station 10a includes a commercial power supply 11a, a
switching device SWa, a charging cable CAa and an ECU 100a.

[0086] The commercial power supply 11 a is a so-called three-phase
four-wire system alternating-current power supply that is widely used in
Europe, and the like. The commercial power supply 11a and the switching
device SWa are connected by power lines Lu, Lv, Lw and a neutral line Ln.
U-phase, V-phase and W-phase alternating-current powers are respectively
supplied to the power lines Lu, Lv and Lw. The potential difference
(phase voltage) between each of the power lines Lu, Lv and Lw and the
neutral line Ln is the voltage V1. The voltage between the power lines
(the potential difference between the power line Lu and the power line
Lv, the potential difference between the power line Lv and the power line
Lw and the potential difference between the power line Lw and the power
line Lu) is the voltage V2. Note that, in the second embodiment, the case
where the voltage V1 is 230 volts and the voltage V2 is 400 volts will be
described as an example.

[0087] The switching device SWa switches the voltage, supplied from the
commercial power supply 11a, to any one of the voltages V1, V2 and V3 and
then supplies the any one of the voltages V1, V2 and V3 to the charging
cable CAa.

[0088] FIG. 11 is a cross-sectional view of the charging cable CAa, taken
along the line XI-XI in FIG. 10. As shown in FIG. 11, the charging cable
CAa is formed so that the power lines Lu, Lv and Lw, the neutral line Ln,
the ground line Lg, and the pilot signal line Lc that extends from the
ECU 100a are tied in a bundle as one cable.

[0089] On the basis of the electric power command value Pcom, the ECU 100a
generates the pilot signal CPLT and then transmits the generated pilot
signal CPLT to the vehicle 1 via the pilot signal line Lc, and also
controls the switching device SWa to set the supply voltage, supplied
from the charging station 10a to the vehicle 1, to any one of the
voltages V1 to V3.

[0090] FIG. 12 shows a first map used to calculate the voltage command
value Vcom and the current command value Icom in the second embodiment.

[0091] Note that, in the following description, P1min, P2min and P3min
respectively denote electric power values when the supply current is a
lower limit value and the supply voltages are the voltages V1, V2 and V3,
and P1max, P2max and P3max respectively denote electric power values when
the supply current is an upper limit value and the supply voltages are
the voltages V1, V2 and V3. In the second embodiment, the voltage V1 is
230 volts, the voltage V2 is 400 volts, the voltage V3 is 400 (three
phase) volts (which is treated as 400 multiplied by 3 (volts) in terms
of electric power), the upper limit value of the supply current is 6
amperes and the lower limit value of the supply current is 12 amperes.
Therefore, P1min is 230 volts multiplied by 6 amperes, P1max is 230 volts
multiplied by 12 amperes, P2min is 400 volts multiplied by 6 amperes,
P2max is 400 volts multiplied by 12 amperes, P3min is 400 multiplied by
3 (volts) being multiplied by 6 amperes and P2max is 400 multiplied by 3
(volts) being multiplied by 12 amperes.

[0092] The ECU 100a according to the second embodiment sets the current
command value Icom and voltage command value Vcom corresponding to the
electric power command value Pcom through the same method as that of the
first embodiment.

[0093] That is, the ECU 100a refers to the first map shown in FIG. 11. The
ECU 100a sets the voltage command value Vcom to the voltage V1 when the
electric power command value Pcom is smaller than a threshold Pb1, sets
the voltage command value Vcom to the voltage V2 when the electric power
command value Pcom falls within the range from the threshold Pb1 to a
threshold Pb2, and sets the voltage command value Vcom to the voltage V3
when the electric power command value Pcom is larger than the threshold
Pb2. Here, the threshold Pb1 is the electric power value P2min (the
product of the voltage V2 and the lower limit value), and the threshold
Pb2 is the electric power value P3min (the product of the voltage V3 and
the lower limit value).

[0094] In addition, the ECU 100a sets the current command value Icom to
Pcom divided by V1 when the electric power command value Pcom falls
within the range from the threshold Pa to the threshold Pb1, sets the
current command value Icom to Pcom divided by V2 when the electric power
command value Pcom falls within the range from the threshold Pb1 to the
threshold Pb2, and sets the current command value Icom to Pcom divided by
V3 when the electric power command value Pcom falls within the range from
the threshold Pb2 to the threshold Pc. Here, the threshold Pa is the
electric power value P1min (the product of the voltage V1 and the lower
limit value), and the threshold Pc is the electric power value P3max (the
product of the voltage V3 and the upper limit value).

[0095] By so doing, the supply voltage may be switched among three levels
(voltages V1, V2 and V3), so further detailed power control is possible.
In addition, because the supply voltage is set to a higher value in a
stepwise manner wherever possible on the condition that the current
command value is not lower than the lower limit value, it is possible to
preferentially set the current command value to a further smaller value,
so loss in process of supplying electric power may be appropriately
suppressed.

[0096] The embodiments described above are illustrative and not
restrictive in all respects. The scope of the invention is defined by the
appended claims rather than the above description. The scope of the
invention is intended to encompass all modifications within the scope of
the appended claims and equivalents thereof